President Donald Trump issued an order Monday evening blocking any merger of the chipmaking giants Broadcom and Qualcomm, saying it was necessary to protect national security. There is “credible evidence,” the order says, that if the Singapore-based Broadcom took control of the US-based Qualcomm that the company “might take action that threatens to impair the national security of the United States.”

Broadcom has been trying to purchase Qualcomm for the last several months, but has continually been rebuffed. It’s since tried to stack Qualcomm’s board with friendly members. Trump’s order says that Broadcom will not be allowed to purchase or merge with Qualcomm in any way, and that all of the people Broadcom has proposed to Qualcomm’s board are disqualified.

It seems that Broadcom was aware that Trump or his Justice Department might attempt to block the merger on these grounds and has been trying to avoid it. Trump has blocked similar takeovers before, having stopped a Chinese state-owned company from buying an American semiconductor firm back in September.

Broadcom is currently in the process of moving its headquarters from Singapore to the US, according to Bloomberg, and planned to complete the transition by April 3rd. With the move, Broadcom seems ready to fight Trump’s order. In a statement, the company said “US national security concerns are not a risk to closing, as Broadcom never plans to acquire Qualcomm before it completes redomiciliation.”

It’s not clear whether that’ll be allowed to happen. Trump’s order says that the two companies should “permanently abandon the proposed takeover,” indicating that Broadcom’s move won’t make a difference, unless it’s willing to take the order to court.